Exhaust gas return means for internal combination engines

ABSTRACT

An intake system for an internal combustion engine in which intake of air and fuel into the combustion chambers is controlled by a throttle valve. An exhaust gas passage recirculates exhaust gas from the exhaust line back into the combustion chamber together with the incoming air. The flow of exhaust gas through such passage is under the control of a shutoff valve, the operating mechanism for which is controlled in response to differences between the pressure prevailing within the intake system and the pressure in the region of the metering element or throttle valve, to open the shutoff valve only during certain predetermined load conditions of the engine.

0 United States Patent 1191 1111 3,713,428 Sandhagen 14 1 Jan. 30, 1973s41 EXHAUST GA S RE'IIUR1 1 MEAAS EQR 2,722,927 11/1955 Cornelius....123/119 A INTERNAL COMBUSTION ENGINES 3,513,816 5/1970 Daigh....123/1l9 A 2,154,417 4/1939 Anderson ..123/119 A [75] Inventor:Jurgen Sandhagen, Fallersleben,

v Germany Primary Examiner-Wendell E. Burns [73] Assignee:Volkswagenwerk Aktiengesellschaft, Assistant Zupclc wombm GermanyAttorneywatson, Cole, Grindle & Watson [21] Appl' 122388 An intakesystem for an internal combustion engine in which intake of air and fuelinto the combustion [30] Foreign Application Priority Data chambers iscontrolled by a throttle valve. An exhaust gas passage recirculatesexhaust gas from the exhaust March ll, Germany line ac into the c b ichamber get e the incoming air. The flow of exhaust gas through [2%]:J.S.((:Zll. ..l2;/11790A Such passage is under the comm] of a shutoffvalve, 0 the ope a ng mechan m fo is con ed n 1e 0 care [119 A responseto differences between the pressure preva" ing within the intake systemand the pressure in the re- [56] References cued gion of the meteringelement or throttle valve, to open UNITED STATES PATENTS the shutoffvalve only during certain predetermined load cond1t1ons of the engme.3,621,825 11/1971 Ojala ..l23/119 A 3,641,989 2/1972 Hill ..123/l19 A 15Claims, 4 Drawing Figures 1, 1s 1 1 17 1 s 11 1 I li g l I 1 l PAIENTEDAN I97 3. 71 3.428

sum 1 or 2 IN VEN TOR BY MW EXHAUST GAS RETURN MEANS FOR INTERNALCOMBUSTION ENGINES This invention relates to improvements in an internalcombustion engine intake system which includes an air metering elementor throttle feeding air or a mixture of fuel and air to the combustionchamber, there being an exhaust line, together with means for the returnof some of the exhaust gas from the exhaust line to the combustionchamber.

While adapted primarily for use in connection with the engine of a motorvehicle, the invention can also be used advantageously in the caseofother engines, for example stationary engines. Furthermore, theinvention is by no means limited to use with carburetor equippedengines, but is adapted as well for use with the intake systems ofengines having direct or indirect fuel injection.

The recycling or return of exhaust gasses through the combustion chamberor chambers of an internal combustion engine, is desirable from thefollowing standpoints.

First, any unburnt components may be in the exhaust gases, such ashydrocarbons and carbon monoxide, are again subjected to the combustionprocess to secure a decrease in the undesirable components of the gasdischarged into the atmosphere. Also, through recycling of the exhaustin this manner there is achieved a reduction of the nitric oxydeemission of the engine, resulting from a decrease of the peak combustiontemperature, so that even during the creation of the exhaust gases,their composition is improved.

It has been found that the return or recycling of the exhaust gas,however, should occur only during certain operational conditions of theengine. Thus, a recycling of the exhaust gas during idling of the engineis generally undesirable, as it may result in certain undesirableinstabilities. Similarly, a recycling of the exhaust gas through thecombustion chamber at full load, is disadvantageous, in many cases, asresulting in a reduction in the performance of the engine.

The invention overcomes the problems of creating an internal combustionengine having an exhaust gas recirculating means and, through aneconomical construction and arrangement of parts, takes into account theforegoing requirements. According to the invention, the return line forthe exhaust gas, bypassing the engine chambers, extends from the exhaustpipe to the intake system. lnterposed in this return line is a shutoffvalve having ,an operating mechanism which is arranged to be responsiveto differences between the pressure prevailing in the induction systemand the pressure in the region of the air metering element or throttlevalve, which pressure varies as the gas velocity is increasedoridecreased due to changes'in the position of the latter. Thearrangement is such that the shutoff valve is opened to permit recyclingof exhaust gases only in the middle or partial load condition of theengine between its idling and heavily loaded conditions.

Thus, in accordance with the present invention, dur ing idling, theshutoff valve is closed. It commences to open at a predetermined minimumload condition of the engine, and is fully opened at the mid-portion ofthe load range. It closes as the engine becomes fully loaded, so thatthe return or recycling of the exhaust gas occurs only between theminimum and maximum load conditions of the engine.

The opposing pressures which control the valve, will change similarlyand simultaneously with changes of atmosphericpressure. The invention,therefore, has the advantage of automatically adjusting to change inatmosphericpressure without requiring provision for adjustment to theparticular altitude at which the given engine operates.

As already mentioned, the pressure in the intake system is automaticallycompared with a second pressure varying in accordance with the positionof the air metering element during idling of the engine. Where the airmetering element is a conventional butterfly throttle valve, the shutoffvalve operating mechanism is responsive, in part, to the pressure in theregion adjacent to the edge of the engine throttle valve, when thelatter is in its idling or nearly closed position. For this reason, theinduction or intake manifold in the region of' the throttle valve has anopening through which the pressure in the region adjacent the edge ofthe throttle valve is transferred to the shutoff valve operatingmechanism.

As a rule, the operating mechanism for the shutoff valve will include atleast one diaphragm which is deflected in response to the differencesbetween the opposing pressures and which, in deflecting, will move theshutoff valve. The preferred design of the invention is characterized bythe fact that the operating mechanism includes two diaphragms, bothoperatively connected to the shutoff .valve stem at spaced-apartlocations and whose relatively remote surfaces are exposed to pressuresin two different pressure chambers. In one chamber, the pressure of theinduction system prevails, and in the other, a second pressure from theregion of the throttle valve prevails. In one of the two pressurechambers, the diaphragm is spring-biased in a direction to close theshutoff valve and it is necessary to overcome the spring pressure inorder to open the shutoff valve.

Also, in accordance with the invention, it is desirable that the shutoffvalve be supported and guided in its movement by the relatively spaceddiaphragms.

Further, in the preferred embodiment, the exhaust gas return passage isformed in several parts or sections, the first of which extends from theexhaust pipe to a first pressure chamber, in which the pressure of theinduction system prevails, and the second of which extends from the saidpressure chamber to the induction system for delivery of exhaust gasesinto the air flowing through the induction system. The valve seat forthe shutoff valve is formed at the port through which the first part ofthe return pipe or passage communicates with the first pressure chamber.In order that the pressure of the exhaust gas acting on the shutoffvalve and on the diaphragms will not impede the operation of that valve,the said port defines a constriction at the entrance to 'the firstchamber.

In order to achieve a compact construction occupying a minimum space,the pressure chambers and shutoff valve, the induction system and theexhaust pipe are combined into a single structural unit in which saidparts are relatively aligned in a common plane, and the first part ofthe return passage is defined by the pipe which extends around theintake manifold in the form of an arch. In accordance with a furtherfeature, the above port, at the junction of the first part of the returnpassage with the first pressure chamber, extends through a connectingblock between the pressure chambers and the induction system, andchannels or passages extend through this block from the first pressurechamber to the air intake system for the purpose of transferring thepressure in the induction system back to the first pressure chamber, aswell as for delivering recycled exhaust gas back into the intakemanifold.

To secure easy accessability to the shutoff valve and its seat for thepurpose of cleaning and servicing, it is desirable to releasably connectthe valve operating mechanism, including the valve itself, with theblock, preferably by means of a threaded connection, in which thethreads are shielded against contact with the exhaust gas.

The preferred embodiment of the invention is illus-- trated by way ofexemplification in the accompanying drawings, in which:

FIG. 1 is a longitudinal section through the invention and the parts ofan engine to which it is applied.

FIGS. 2 and 3 are sectional views along the lines II II and III III,respectively, of FIG. 1.

FIG. 4 is a diagrammatic illustration of the throttle valve of theinternal combustion engine and the way in which it communicates with thesecond pressure chamber.

Referring now in detail to the accompanying drawings, the block 3, theinduction or intake manifold 4, and the exhaust gas-pipe 5, preferablyare aligned in a common plane represented by the line 1 of FIG. 1, andextending through the operating mechanism 2. The exhaust pipe 5 and theair intake manifold 4 are connected with one another through an exhaustgas return passage under the control of the tappet valve 6. The exhaustgas return passage comprises two parts designated 7 and 8, in additionto the port 9 and chamber 19. The first part 7 of this passage isdefined by a pipe which partially encircles the induction manifoldsystem 4 in the form of an arch, while the second part 8 of the returnpassage extends preferably in a straight line through the block 3 andestablishes communication between the pressure chamber 19 and the intakemanifold 4. The port 9 leading into the pressure chamber 19 is ofsmaller diameter than the passage 7, to serve as a restricter, while theblock 3 around the upper end of the port 9 constitutes a concave valveseat for the valve 6. The end surface 11 of the valve 6 iscorrespondingly formed in a convex manner to secure a self centering ofthe valve with regard to its seat.

The valve 6 is supported and guided for operative movement by the twodiaphragms 12 and 13, it being noted that the valve stem extends influid-tight manner through and is connected to both diaphragms. Theouter peripheries of the respective diaphragms 12 and 13 are supportedin a fluid-tight manner, respectively, between registering annularportions of the valve housing or casing 14 and the clamping rings 15 and16.

The entire valve operating mechanism 2 is releasably connected to theblock 3 by means of a nut 17 which iswelded to the casing or housing 14in a manner to achieve greatstability. It is to be noted that the threadof nut 17 is isolated from chamber 19 by gasket 18 and thus is shieldedfrom the exhaust gas when the latter passes through chamber 19.

The two diaphragms l2 and 13, respectively, constitute deflectable wallsof the two pressure chambers 19 and 20, of which the first pressurechamber 19 is at all times connected with the intake manifold 4 by wayof the channel or passage 8, so that the intake pressure prevails inchamber 19, while (referring jointly to FIGS. 1 and 4), the other orsecond pressure chamber 20 is connected by way of pipe 21 with anopening 23 in the intake manifold in the region closely adjacent theedge of the conventional engine throttle valve 24 in the form of a discwhich is medially fulcrumed at 25 within the intake manifold or passage4, for rotary adjustment about an axis 25 disposed diametrically to thepassage 4. It will be noted that the pipe or conduit 21 opens into theintake manifold or passage 4 at a location 23 which is closely adjacentthe edge of the butterfly throttle valve 23 when the latter is justslightly open or at its idling position, substantially as shown in fulllines in FIG. 4, so that the throttle valve, at this time, coats withthe casing 4 in defining a restricted passage adjacent the opening 23,through which the air must pass at an accelerated velocity and,therefore, at a lowered pressure. This lowered pressure is communicatedto the second pressure chamber 20 through the pipe 21. Also, in thesecond compression chamber 20 is housed the compression spring 22 whichexerts a pressure tending to seat the lower end of the valve 6 againstthe valve seat 10.

The relative pressures in the two chambers 19 and 20, therefore, changein accordance with the operating conditions of the engine. Thus, thepressure in the first pressure chamber 19 is higher than that in thesecond pressure chamber 20, whenever the engine is operated at or near ano load condition.

However, the area of diaphragm 12 exposed to pressure within the chamber19 is less than the area of diaphragm 13 exposed to pressure within thesecond pressure chamber 20. The strength of the spring 22 is such thatas loading of the engine commences, the valve 6 will be lifted slightlyoff the valve seat 10 to permit a small recycling flow of exhaust gasfrom the exhaust pipe 5 through passage 7, port 9, pressure chamber 19and passage 8, into the intake manifold 4. With an increasing load, thetwo pressure values approach each other until they become equalizedsubstantially at the mid-load range of the engine, at which time thevalve 6 is fully opened to recycle a maximum amount of exhaust gasesthrough the combustion chamber. As the load on the engine approaches orreaches full load, the two pressure values within the chambers 19 and 20remain practically equalized, but decrease so considerably that theforce of the spring 22 prevails and closes the valve 6 to discontinuethe recycling of exhaust gases.

Thus, in accordance with the invention, it will be seen that the returnor recycling of the exhaust through the combustion chambers by way ofthe return passage 7, 8, will occur only when the engine is operatedthrough the medial portion of its load range.

Having thus described my invention, I claim:

1. In an internal combustion engine with an intake manifold containingan air metering element for feeding a mixture to the combustionchambers, and an exhaust gas pipe, and means for the return of theexhaust gas to the combustion chambers, the improvement which comprisesmeans defining an exhaust gas return passage (7, 8) for deliveringexhaust gas from the exhaust gas pipe (5) to the intake manifold (4), ashutoff valve (2, 6) controlling the flow of exhaust gas through saidpassage (7, 8), and valve operating mechanism responsive to differencesbetween the pressure in the intake manifold and the pressure in theregion of the air metering element to open the shutoff valve (6) only inthe means partial load operation of the engine.

2. An internal combustion engine according to claim 1, characterized inthat the air metering element is a throttle valve and the operatingmechanism (2) is fed the pressure in the area of the edge of thethrottle valve in its position during idling.

3. An internal combustion engine according to claim 1, characterized inthat the operating mechanism (2) comprises two diaphragms (12, 13)supporting a tappet valve (6) for operative movement, said diaphragmsrespectively cooperating with pressure chambers (19, 20) in one of whichthe pressure of the intake manifold (4) prevails and in the other ofwhich another pressure prevails.

4. An internal combustion engine according to claim 3, characterized inthat a spring (22) forcing the shutoff valve (6) in the direction of thevalve seat has been disposed in one of the two pressure chambers (13,20), the strength of said spring and the relative areas of therespective diaphragms being such that only in the event of equality ofthe two pressures in the said chambers is the valve (6) opened.

5. An internal combustion engine according to claim 4, characterized inthat the valve (6) is suspended movably by means of diaphragms (l2, l3),and is formed for self-centering engagement with a valve seat (10). a

6. An internal combustion engine according to claim 5, characterized inthat said valve (6) is formed with a convex end (11) and the valve seat(10) is concave.

7. An internal combustion engine according to claim 3, characterized inthat the return passage comprises two parts (7, 8), the first of which(7) extends from the exhaust pipe (5) up to the first pressure chamber(19) in which the pressure of the induction system (4) prevails and thesecond part (8) extends from this pressure chamber (19) to the inductionsystem (4), and in that the valve seat (10) is formed at the junction(9) of the first part (7) of the return passage with the first pressurechamber (19).

8. An internal combustion engine according to claim 7, characterized inthat the first part (7) of the return pipe contains a restrictor in thefonn of a valve part 9 adjacent to the valve seat (10).

9. An internal combustion engine according to claim 7, characterized inthat the pressure chambers (19, 20), the valve (6), the intake manifold(4), and the exhaust gas pipe (5) are disposed in a common plane (I) andthat the first part (7) of the return pipe encirlces the cross-sectionof the intake manifold (4) in the form of an arc.

10. An internal combustion engine according to claim 9, characterized inthat the junction (9) of the first part (7) of the return pipe comprisesa valve part defined by a connecting block (3) between the pressurechambers (19, 20) and the intake system (4), said block (3) being formedwith a channel (8) for transferring the pressure in the intake system 4to the adjoining pressure chamber (19).

An mterna combustion engine according to claim 10, characterized in thatthe valve operating mechanism (2) including the valve (6) is releasablyassociated with the block (3).

12. An internal combustion engine according to claim 11, characterizedin that said valve operating mechanism is connected to the block (3) byway of screw connections (17) shielded against contact with the exhaustgas.

13. In an internal combustion engine having an intake manifolddelivering air from the atmosphere into its combustion chamber, athrottle valve in said manifold for controlling the flow of airtherethrough, an exhaust pipe for discharging exhaust gases from thecombustion chambers, and means defining an exhaust gas return passagefor establishing communication between the exhaust pipe and said intakemanifold, a shutoff valve controlling the flow of exhaust gases throughsaid return passage and means for operating said valve in response tovarying differences between the pressure prevailing within said manifoldin the region of said throttle valve and the pressure within saidmanifold remote from said throttle valve.

14. The combination defined in claim 13, including resilient meansconstantly urging the said shutoff valve toward closed position.

15. The combination of claim 13 further including a housing for saidshutoff valve, flexible diaphragm means within said housing dividingsame into first and second pressure chambers, said diaphragm means beingsubjected to the opposing pressures in the respective chambers, saidfirst pressure chamber being interposed in said exhaust return passageand including a valve seat for cooperation with said shutoff valve, saidseat defining a valve port constituting a part of said exhaust gaspassage, said shutoff valve being a tappet valve carried by saiddiaphragm means for movement into and from seating relation with saidvalve seat to control the flow of exhaust gases through said returnpassage; said second pressure chamber communicating with said intakemanifold in the region of said throttle valve to be subjected to changesin pressure in response to changes in the operating position of saidthrottle valve.

* a: t k

1. In an internal combustion engine with an intake manifold containing an air metering element for feeding a mixture to the combustion chambers, and an exhaust gas pipe, and means for the return of the exhaust gas to the combustion chambers, the improvement which comprises means defining an exhaust gas return passage (7, 8) for delivering exhaust gas from the exhaust gas pipe (5) to the intake manifold (4), a shutoff valve (2, 6) controlling the flow of exhaust gas through said passage (7, 8), and valve operating mechanism responsive to differences between the pressure in the intake manifold and the pressure in the region of the air metering element to open the shutoff valve (6) only in the means partial load operation of the engine.
 1. In an internal combustion engine with an intake manifold containing an air metering element for feeding a mixture to the combustion chambers, and an exhaust gas pipe, and means for the return of the exhaust gas to the combustion chambers, the improvement which comprises means defining an exhaust gas return passage (7, 8) for delivering exhaust gas from the exhaust gas pipe (5) to the intake manifold (4), a shutoff valve (2, 6) controlling the flow of exhaust gas through said passage (7, 8), and valve operating mechanism responsive to differences between the pressure in the intake manifold and the pressure in the region of the air metering element to open the shutoff valve (6) only in the means partial load operation of the engine.
 2. An internal combustion engine according to claim 1, characterized in that the air metering element is a throttle valve and the operating mechanism (2) is fed the pressure in the area of the edge of the throttle valve in its position during idling.
 3. An internal combustion engine according to claim 1, characterized in that the operating mechanism (2) comprises two diaphragms (12, 13) supporting a tappet valve (6) for operative movement, said diaphragms respectively cooperating with pressure chambers (19, 20) in one of which the pressure of the intake manifold (4) prevails and in the other of which another pressure prevails.
 4. An internal combustion engine according to claim 3, characterized in that a spring (22) forcing the shut-off valve (6) in the direction of the valve seat (10), has been disposed in one (20) of the two pressure chambers (13, 20), the strength of said spring and the relative areas of the respective diaphragms bEing such that only in the event of equality of the two pressures in the said chambers is the valve (6) opened.
 5. An internal combustion engine according to claim 4, characterized in that the valve (6) is suspended movably by means of diaphragms (12, 13), and is formed for self-centering engagement with a valve seat (10).
 6. An internal combustion engine according to claim 5, characterized in that said valve (6) is formed with a convex end (11) and the valve seat (10) is concave.
 7. An internal combustion engine according to claim 3, characterized in that the return passage comprises two parts (7, 8), the first of which (7) extends from the exhaust pipe (5) up to the first pressure chamber (19) in which the pressure of the induction system (4) prevails and the second part (8) extends from this pressure chamber (19) to the induction system (4), and in that the valve seat (10) is formed at the junction (9) of the first part (7) of the return passage with the first pressure chamber (19).
 8. An internal combustion engine according to claim 7, characterized in that the first part (7) of the return pipe contains a restrictor in the form of a valve part 9 adjacent to the valve seat (10).
 9. An internal combustion engine according to claim 7, characterized in that the pressure chambers (19, 20), the valve (6), the intake manifold (4), and the exhaust gas pipe (5) are disposed in a common plane (1) and that the first part (7) of the return pipe encirlces the cross-section of the intake manifold (4) in the form of an arc.
 10. An internal combustion engine according to claim 9, characterized in that the junction (9) of the first part (7) of the return pipe comprises a valve part defined by a connecting block (3) between the pressure chambers (19, 20) and the intake system (4), said block (3) being formed with a channel (8) for transferring the pressure in the intake system 4 to the adjoining pressure chamber (19).
 11. An internal combustion engine according to claim 10, characterized in that the valve operating mechanism (2) including the valve (6) is releasably associated with the block (3).
 12. An internal combustion engine according to claim 11, characterized in that said valve operating mechanism is connected to the block (3) by way of screw connections (17) shielded against contact with the exhaust gas.
 13. In an internal combustion engine having an intake manifold delivering air from the atmosphere into its combustion chamber, a throttle valve in said manifold for controlling the flow of air therethrough, an exhaust pipe for discharging exhaust gases from the combustion chambers, and means defining an exhaust gas return passage for establishing communication between the exhaust pipe and said intake manifold, a shutoff valve controlling the flow of exhaust gases through said return passage and means for operating said valve in response to varying differences between the pressure prevailing within said manifold in the region of said throttle valve and the pressure within said manifold remote from said throttle valve.
 14. The combination defined in claim 13, including resilient means constantly urging the said shutoff valve toward closed position. 